New Shoes... And i'm confused...

[iantz Avid PP Poster! Find all posts View Profile Close iantz]

Ok, I've spent quite a bit of time reading the threads here on PP regarding new rubber. I've finally worn down the GrandCraps and have been looking around for replacements. I will either be going with Dueler 694 LT, or BFG A/Ts.

The issue of tyre sizing is confusing. From my understanding, you can't increase tire diameter more than 15mm in SA (and I'm pretty sure elsewhere).

So, first question: 1) Am I right in concluding that BFG 265/70/17 increases overall tire diameter by by approximately 26mm, which subsequently means it doesn't comply with regs and is ultimately illegal?
2) Dueler 694LTs in 275/65/17 are legal because they increase overall diameter by about 13mm, therefore coming in under the 15mm allowance?

The point with the second question here is that i've been reading up on mods and apparently, I can only increase ride height by 50mm. This includes both increases due to tyre change and suspension. So, even though the 694s in 275/65 are legal, as soon as I raise my suspension (in about 2 months), I will have exceeded the 50mm overall limit right?

So, can someone confirm that my reasoning here is correct? Is it the case that if I want a lift then I am going to have to stick with 265/65? If I were to get a CPE certificate for the larger tyres, do you know if I would then be able to legally lift by another 50mm with suspension?

Excuse my rambling here guys, but I am finally starting to mod the prado and the more I read the more confused I get. Most questions I have I've found answers for, but just thought i'd throw these questions out there for clarification because i think my conclusions are correct???

Thanks in advance -
Ian.

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Re: New Shoes... And i'm confused...

In summary (and you have already got to this point):
265/70R17 is illegal
275/65R17 is legal

As for ride height, I'm not too sure about but I thought that the 50mm increase is in suspension height. Any increase in tyre diameter is a separate issue. Those with better ADR knowledge can confirm. I tried Googling but haven't found the right documents to look at (yet).

I know that in NSW, any change in suspension ride height up to 50mm requires an engineer's certificate.

[iantz Avid PP Poster! Find all posts View Profile Close iantz]

Re: New Shoes... And i'm confused...

Thanks for the info AMTS

I thought the same regarding tyres and suspension (different regs), but then I found the following vehicle specifications document.

http://www.transport.sa.gov.au/pdfs/per ... Height.PDF

Taken from this page

http://www.transport.sa.gov.au/personal ... hicles.asp

You will see on page 2 that a vehicle can be raised by a maximum of 50mm, using a combination of Tyres, Suspension, and Body Lift. So, based on this doc, increase in height due to tyres is taken into account in overall raise, so larger tyres + lift = Illegal, but standard tyre size + lift = Legal. This is my interpretation anyway and it seems to be the correct one.

To go over this height you need a certificate. But, for the sake of 14mm which is all you would achieve using a larger tyre, the cost of these certificates and associated insurance hassles are probably not worth it????

[timmay5.7 Advanced Member Find all posts View Profile Close timmay5.7]

Re: New Shoes... And i'm confused...

To go over this height you need a certificate. But, for the sake of 14mm which is all you would achieve using a larger tyre, the cost of these certificates and associated insurance hassles are probably not worth it????

Until you get inspected, or have an accident...

[iantz Avid PP Poster! Find all posts View Profile Close iantz]

Re: New Shoes... And i'm confused...

Timmay - that's my point. I've probably written my response a little wrong. I won't drive a car that is not insured. So, the cost of the certificate in order to 'make it legal' probably isn't worth the 14mm that I get from bigger tyres. In other words, forget the tyres (stick with 265/65) and go the lift. A good increase in height but still legal (without need for certificates etc....)

Cheers
Ian.

[Hutch Addicted PP Member Find all posts View Profile Close Hutch]

Re: New Shoes... And i'm confused...

Both those tyres mentioned have a 265/65 option so why not just stick with them and have no issues.

[iantz Avid PP Poster! Find all posts View Profile Close iantz]

Re: New Shoes... And i'm confused...

Hutch - I was told that the BFG in that size is not LT? I like the more aggressive look of the BFG over the Dueler so if their build quality is good i'd go for it. I got a price of $340 each on BFG 265/65. Not a bad price I think?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Re: New Shoes... And i'm confused...

For a 14mm increase in diameter you are increasing axle height by a maximum of half this (7mm), less tyre bulge etc. Then are you sure you will have 50mm lift from the suspension. What about sag? Check with others who have the suspension fitted and see what height their suspension has settled to. I have both the 275s and a 50mm lift but the regs here are a bit different and refer to bump stop measurements rather than an outright limit on lift.

[Hutch Addicted PP Member Find all posts View Profile Close Hutch]

Re: New Shoes... And i'm confused...

Hutch - I was told that the BFG in that size is not LT? I like the more aggressive look of the BFG over the Dueler so if their build quality is good i'd go for it. I got a price of $340 each on BFG 265/65. Not a bad price I think?

The BFG is Light truck, the 694 can be had in LT and passenger in that size. Have a look at the tyre the sidewall will read lt265/65 vs p265/65

[Way2go Member Find all posts View Profile Close Way2go]

Re: New Shoes... And i'm confused...

I know that in NSW, any change in suspension ride height up to 50mm requires an engineer's certificate.

From past experience, I believe it's a change in suspension ride height over 50mm requires an engineers certificate.

Under VSI 06 - "Generally, roll stabilizer bars, axle locating rods, upgraded shock absorbers or upgraded springs may be used provided they are suitable for the vehicle and are properly fitted."

Under the NCOP (still to be ratified by the states) the 50mm lift allowed definitely takes into account larger tyres, suspension lift and body lift.

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Re: New Shoes... And i'm confused...

From past experience, I believe it's a change in suspension ride height over 50mm requires an engineers certificate.

I thought the new ruling came through last year
http://www.themotorreport.com.au/37361/ ... suspension

Under the NCOP (still to be ratified by the states) the 50mm lift allowed definitely takes into account larger tyres, suspension lift and body lift.

That's a bummer.

[iantz Avid PP Poster! Find all posts View Profile Close iantz]

Re: New Shoes... And i'm confused...

mjrandom -

Thanks for your thoughts. I agree that ride height is only increased by 7mm. So, even with the lift, after a bit of sag, I probably would only *just* be bordering the 50mm.

Unfortunately, these are the rules for tyres

The fitting of rims with a different diameter to those listed on the vehicle’s tyre placard is acceptable, provided that the overall diameter of the alternative rim/tyre combination is not greater than 15mm over the largest combination or 15mm smaller than the smallest combination specified on the vehicle’s tyre placard.

This is taken from my link posted above. So, in terms of the BFG, I will still exceed this limit. However, for the Dueler, I can go the 275/65, because they are only lifting ride height by 7mm, so after a little bit of sag after a 2" lift I should be well under the 50mm (or i'll just add . So, it seems I should be good to go with this.

Out of interest, I spoke with Cooper tyres today. They said that their recommendation for the Prado would be the 245/70/17 in ST or STT. The overall diameter difference is about =3mm. barely noticeable. They also suggested that because the coopers are very broad in the shoulder, that the difference in width (in terms of actual road contact) isn't actually 20mm.

What do people think about a more aggressive tyre such as the STT in the slightly slimmer version? I am losing much by reducing width?

Cheers
Ian.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Re: New Shoes... And i'm confused...

Ian not sure what you perceive the difference to be, the BFG A/Ts I was talking about are also 275/65 17 and fall (just) within the legal limitations.

Michael

[Hutch Addicted PP Member Find all posts View Profile Close Hutch]

Re: New Shoes... And i'm confused...

mjrandom -

Thanks for your thoughts. I agree that ride height is only increased by 7mm. So, even with the lift, after a bit of sag, I probably would only *just* be bordering the 50mm.

Unfortunately, these are the rules for tyres

The fitting of rims with a different diameter to those listed on the vehicle’s tyre placard is acceptable, provided that the overall diameter of the alternative rim/tyre combination is not greater than 15mm over the largest combination or 15mm smaller than the smallest combination specified on the vehicle’s tyre placard.

This is taken from my link posted above. So, in terms of the BFG, I will still exceed this limit. However, for the Dueler, I can go the 275/65, because they are only lifting ride height by 7mm, so after a little bit of sag after a 2" lift I should be well under the 50mm (or i'll just add . So, it seems I should be good to go with this.

Out of interest, I spoke with Cooper tyres today. They said that their recommendation for the Prado would be the 245/70/17 in ST or STT. The overall diameter difference is about =3mm. barely noticeable. They also suggested that because the coopers are very broad in the shoulder, that the difference in width (in terms of actual road contact) isn't actually 20mm.

What do people think about a more aggressive tyre such as the STT in the slightly slimmer version? I am losing much by reducing width?

Cheers
Ian.

The 245/70 stt or st compared to a Dunlop at20 tread width on road is pretty much identical as the shoulder of the AT20 is very rounded, i have also explored this option but have no justification to buy a set.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Re: New Shoes... And i'm confused...

Hutch is absolutely spot on. The 245 or 265 or 275 refers to the widest point of the tyre. The treadwidth on my 275/65 17 BFG A/Ts is about 225mm from memory. If the tyre has a square shoulder like the STTs etc then the tread width will be closer to the tyre size. A rounder shoulder and pattern like the AT20s (car tyre construction) will mean more sidewall and less tread. For example there will be little if any difference in tread width between the 265 and 275 BFG A/Ts. What you gain is a little more sidewall height (7mm) and a bit wider cross section which is useful in sand. The width of the tread will depend entirely on the tyre as it varies. The P Zeroes on my Clubbie are also 275s but the tread width is about 270mm because the profile is only 30% (275/30 20) and there isn't much sidewall. Or tread (at the moment ops: )

245/70 17 mud terrains (MT) are pretty much exactly the same diameter as 265/65 17 so there are no worries in that regard and being a 70 profile tyre I would expect the load rating to be higher because the 70 profile tyres will be LT construction. There are a few LT 65s getting around and the BFGs for one are light truck construction. Check if the sizing includes the letters LT.

Most of this has been done to death in this forum and fairly recently in this thread viewtopic.php?f=22&t=8904 you can use the tyre size calculator and check the differences.

The downside of MT tyres though is usually shorter life because the more prominant knobs on the tyre twist and squirm; probable harsher ride because the sidewalls will likely have more plies than an A/T type tyre but again this varies; noisier on the road because of the fewer, larger knobs; and they are not much fun on sand as they don't bag as much as an A/T type tyre and they tend to dig in. Badly. If I was spending most of my time driving in mud and rocky terrain I would have 245/70 17 mud tyres on board but I mainly do beach, fire trail and road driving so the A/T suits me fine.

Some people have gone to the trouble of having two sets of tyres. AT20s or similar for the road and MT or A/T tyres for 4wding. I don't have that sort of budget so I settle for an A/T tyre.

Michael